Atropine|Structure|Synthesis|MOA|Uses|Side effects|deadly nightshade|Atropa Belladonna

Nalidixic acid 

Nalidixic acid is a pioneering antibacterial agent, recognized as the first synthetic quinolone antibiotic. It played a foundational role in the development of modern fluoroquinolones and has been widely used to treat urinary tract infections (UTIs) caused by Gram-negative bacteria. Discovered in the 1960s, this compound has been a reliable choice in clinical settings, especially in infections involving E.coli and other urinary pathogens.

It is a white to slightly yellow crystalline powder that is odorless. Nalidixic acid is insoluble in water, which poses certain limitations in formulation, but is manageable with appropriate pharmaceutical techniques. The melting point of nalidixic acid is  445⁰F (229⁰C), indicating high thermal stability. The molecular weight of nalidixic acid is 232.23 g/mol. 

Nalidixic Acid is also marketed under several brand names and synonyms, including Uronidix, Innoxalon, Betaxina, Urisal, Nogram, Navigramon, etc.

Chemical Structure of Nalidixic Acid:-

• The molecular formula of nalidixic acid is  [C12H12N2O3].

Structure of Nalidixic Acid

• The IUPAC name of nalidixic acid is 1-ethyl-7-methyl-4-oxo-1,8-naphthyridine-3-carboxylic acid.

Mechanism of Action: How Nalidixic Acid Works

One of the critical aspects of any antibiotic is how it targets bacteria. Nalidixic Acid exhibits its bactericidal activity by interfering with bacterial DNA replication.

Upon administration, nalidixic acid is converted into its active metabolite-hydroxynalidixic acid. The metabolite reversibly binds to DNA gyrase, an essential enzyme in bacterial DNA replication and transcription. DNA gyrase introduces negative supercoils into DNA to relieve the torsional strain during replication. By inhibiting this enzyme, nalidixic acid prevents DNA from unwinding and copying, ultimately leading to the cessation of bacterial growth and death.

Additionally, it hampers RNA synthesis and protein production, further disrupting vital bacterial infections. This action is highly selective for gram-negative organisms, especially those residing in the urinary tract.

Clinical and Therapeutic Uses of Nalidixic Acid:-

The primary use of nalidixic acid is in the treatment of urinary tract infections (UTIs). it is particularly effective against:

1.  E.coli
2. Enterobacter species
3. Proteus species.
4. Klebsiella species (in some cases)

Due to its limited activity against Gram-positive bacteria and Pseudomonas aeruginosa, it is not recommended for broad-spectrum antibacterial therapy. However, it remains a valuable option for uncomplicated UTIs where resistance is low.

In certain religions, nalidixic acid is also used to treat gastrointestinal infections, particularly those caused by susceptible strains of Shigella and Salmonella; however, this is less common due to the emergence of resistance and the availability of better alternatives.

Side effects of Nalidixic Acid:-

Like all medications, nalidixic acid can cause adverse reactions, particularly when misused or taken in high doses. Common side effects include

1. Rash
2. Hives and skin rash
3. Itching
4. Difficulty in breathing
5. Tightness in the chest
6. Blurred vision
7. Tingling sensetion
8. Change in color vision
9. Convulsion
10. Diarrhea
11. Headache
12. Nausea and vomiting

Patients with liver or kidney impairment, or those taking anticoagulants or anti-epileptic drugs, should consult their physician before use. Nalidixic acid is contraindicated in infants under 3 months and should be used cautiously in pregnant or breastfeeding women.

Dosage and Administration of Nalidixic Acid:-

The typical adult dosage for treating UTIs is 500 to 1000 mg four times daily, depending on the severity of the infection and the patient's condition. It is usually prescribed for 7 to 14 days, and the patients are advised to complete the full course to prevent resistance.

Food may interfere with absorption, so it is often taken on an empty stomach with water. Adequate hydration is essential to avoid crystal formation in urine.

Conclusion:-

 Nalidixic acid remains an important antibiotic in the history of antimicrobial therapy. As the first member of the quinolone class, it laid the groundwork for modern fluoroquinolones. While its uses have declined due to the resistance and availability of superior alternatives. It still holds clinical relevance for uncomplicated urinary tract infections caused by sensitive gram-negative bacteria.

Frequently Asked Questions (FAQs):-

1. What is nalidixic acid primarily used for?

    The primary use of nalidixic acid is in the treatment of urinary tract infections (UTIs).

2. Is nalidixic acid effective against all kinds of bacteria?

    No, it is primarily active against gram-negative organisms and has no activity against gram-positive        bacteria.

3. Can children take nalidixic acid?

    Nalidixic acid is contraindicated in infants under 3 months and should be used cautiously                      in pregnant or breastfeeding women.

4. Are there any drug interactions with nalidixic acid?

    Yes, it can interact with blood thinners like warfarin, antacids, and antiepileptic drugs. Always                inform your doctor about other medications you are taking.